If you want to achieve optimum growth for your fish, you should feed them a pelletised ration that has been formulated for that particular species. You can buy native fish pellets from feed stores.
If you would prefer a more natural diet, and you are prepared to accept slower growth rates, you may be able to supplement your pellets with duckweed (Lemna Spp) or Azolla. You can also feed worms, mealworms or other live food.